The Tool Desk
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If repeated attempts still fail, ask the requesting service for its exception-handling or alternate-identification process. Authentication is not the only permitted way to identify yourself when technical, biometric, illness, injury, infirmity, or other specified problems prevent a match.
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Read the error code before trying again
UIDAI displays authentication failures with an error code. Its resident FAQ advises taking that code to the concerned entity so the entity can diagnose the failed transaction. Write down the code, the service you were using, whether you selected OTP or biometrics, and the approximate time of the attempt. A screenshot is useful if it does not expose your full Aadhaar number or OTP.
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| Code | Failure category | First action |
|---|---|---|
| 400 | OTP validation failed or the OTP is invalid | Use the current six-digit OTP; request a new one after repeated failures. |
| 402 | Transaction mismatch | Restart the transaction so the OTP and transaction ID come from the same request. |
| 403 | Attempt limit reached or no OTP was generated | Generate a fresh OTP and retry from a new transaction. |
| 740 | OTP data is missing | Wait for the OTP response and enter all six digits before submitting. |
| 952 | OTP flooding | Stop requesting codes and wait before asking for another. |
| 504 | Session key expired or is out of sync | Discard the stale session and begin again through the service. |
| 998 | Invalid Aadhaar number or data unavailable | Check the Aadhaar number format and ask the service to verify the record. |
The table is a triage guide, not a replacement for the exact message on your screen. A service may show an additional description alongside the UIDAI code, and that description can indicate whether you should wait, restart, or contact the operator.
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Five-minute triage before another attempt
- Capture the context. Note the code, the service or portal name, the selected authentication method, and the time. Do not keep pressing Submit while you are still identifying the problem.
- Check which factor you used. OTP errors require a different fix from fingerprint, iris, or face-authentication failures. If you switched methods midway, start a new transaction rather than combining the two attempts.
- Check connectivity. A weak connection can delay the OTP response. Wait for the response instead of refreshing the page, pressing Back, or opening several parallel requests.
- Use one active session. Keep the original transaction window open until it finishes or clearly reports an error. A second tab or a refreshed page can create a different session and invalidate the first one.
- Follow the code-specific branch. Use the OTP, timeout, biometric, or Aadhaar-number instructions below. If the same code returns after the prescribed action, save it for escalation instead of repeating an identical attempt indefinitely.
Fix invalid or failed OTP errors
Error 400: invalid OTP or OTP validation failed
Error 400 means the OTP submitted did not validate. Enter the six-digit code from the most recent OTP request, not a code from an earlier request. If you requested several codes, an older message may arrive after a newer one; use the code associated with the active transaction.
- Return to the original authentication screen without refreshing it.
- Enter all six digits of the latest OTP exactly as received.
- Submit once and wait for the result.
- If repeated attempts produce error 400, request a fresh OTP and use that new code. Do not continue submitting the same rejected code.
If the service generated a new transaction while you were waiting, the latest OTP may belong to that new transaction. In that case, cancel the stale attempt and begin again so the displayed transaction and OTP are paired.
Error 402: transaction mismatch
Error 402 indicates that the OTP and the transaction identifier do not belong to the same authentication request. This can happen after a page refresh, a Back-button action, a second tab, or a delayed response that caused the service to start another session.
- Exit or cancel the current authentication attempt using the service’s own control.
- Return to the service’s Aadhaar-authentication step and start a completely new transaction.
- Request one OTP from that new transaction and submit it in the same window.
- Do not copy an OTP from an earlier attempt into the restarted transaction.
Error 403: attempts exceeded or no OTP generated
UIDAI’s error table uses 403 for an exceeded attempt condition or a situation in which no OTP was generated. Generate a fresh OTP from a new transaction and retry. If the service immediately returns 403 again, stop submitting requests and contact the service operator with the code and timestamp; repeated presses can create additional limits rather than resolve the underlying problem.
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Error 740: missing OTP data
Error 740 means the OTP data was not present when the request was submitted. The response may simply be delayed. Keep the transaction open until the OTP response arrives, enter all six digits, and only then submit. Do not press Refresh or Back while waiting, because either action can start another session and leave the original response unusable.
Error 952: OTP flooding
Error 952 is an OTP-flooding condition. UIDAI’s advisory describes it as more than one OTP generation within 30 seconds and recommends a longer interval between resend requests.
- Stop pressing “Resend OTP” and close any duplicate authentication tabs.
- Wait longer than the minimum resend interval before requesting another code. The exact release time can depend on the service and its transaction state.
- When you request again, use the resulting OTP in the still-active transaction and submit it once.
- If 952 persists after waiting, give the service provider the code and the times of your requests so it can clear or restart the transaction.
Prevent timeout and stale-session failures
A timeout is often a session problem rather than a bad Aadhaar number. UIDAI explains that Refresh or Back can commence a new session, while poor connectivity can prevent an OTP from being generated in time. The API specification documents error 504 for a session-key expiry or a key that is out of sync.
Use a single, uninterrupted transaction
- Open the authentication page once and leave it in the foreground while the request is processed.
- Do not refresh, press Back, or submit repeatedly while waiting for an OTP or biometric result.
- Do not use an OTP from a previous tab, previous attempt, or different service request.
- If the page clearly times out, start again from the service’s beginning rather than trying to revive the expired page.
Handle a 504 or session-key message
For error 504, the active session is no longer usable because its key expired or is out of sync. Record the code, abandon that session, and start a new authentication transaction through the requesting service. If a new transaction repeatedly ends in 504, the service operator may need to correct its integration or clear a server-side session; provide the operator with the time and exact wording instead of continuing to retry.
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Reduce delays caused by connectivity
Move to a more reliable connection if the OTP request is taking unusually long, then begin a fresh transaction. Changing connectivity while an old request is still open can leave two sessions competing; finish or cancel the old attempt first. Never assume that pressing Resend immediately is harmless: rapid requests can produce error 952.
Fix biometric authentication failure
Biometric authentication can use a fingerprint, iris, or face modality. For a fingerprint failure, correct the physical capture conditions before assuming that the Aadhaar record is wrong.
- Clean the finger. Remove dirt, excess moisture, or residue that could interfere with the sensor.
- Clean the scanner. The operator should ensure the capture surface is free of smears or debris.
- Use the instructed placement and pressure. Place the finger as directed and apply steady, moderate pressure rather than moving it during capture.
- Try another enrolled finger. A different finger can produce a better match if the first one is worn, wet, or difficult for the device to read.
- Retry through a new capture request if the first session has failed. Do not keep submitting against a timed-out transaction.
If biometric failures continue over a period of time despite clean equipment, correct placement, and another finger, visit an Aadhaar update centre to update your biometrics. Ask the service whether it can use another supported modality or its exception process while the update is pending.
Check the Aadhaar number for error 998
UIDAI identifies error 998 as an invalid Aadhaar number or unavailable data. First validate the number format before submitting it again. Enter the intended 12-digit Aadhaar number carefully, without accidentally transposing digits or using a number from another document. If the format is correct and 998 continues, the requesting entity should investigate whether the data is unavailable to its system; repeated re-entry will not repair a backend availability problem.
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Keep the displayed code and the time of the failure. When you contact the service, ask it to verify the number through its authorized process rather than sending your full Aadhaar number through an unsecured email, chat, or social-media message.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Choose another authentication modality when available
UIDAI confirms that authentication can use OTP, fingerprint, iris, or face modalities. The practical choice depends on what is available at the point of service and on the reason the first method failed.
| Method | What you need | Prefer it when | Important limitation |
|---|---|---|---|
| OTP | Access to the mobile number registered for Aadhaar and a functioning transaction session | Your registered mobile is available and biometric capture is inconvenient | It depends on delivery of the current OTP; repeated requests can trigger flooding controls. |
| Fingerprint | A supported scanner and a finger that can be captured clearly | The operator has reliable equipment and your fingerprint reads consistently | A poor capture or repeated biometric mismatch can require another finger or a biometric update. |
| Iris | A supported iris-capture device and a successful scan | Fingerprint capture is not producing a match and the provider offers iris authentication | It is available only where the provider and device support the modality. |
| Face | A provider that offers face authentication and compatible capture | The service presents face authentication as an available alternative | Availability is controlled by the requesting service; it is not a universal fallback on every portal. |
Before switching methods, ask the operator whether changing modalities will create a new transaction. If it will, let the first transaction finish or be cancelled, then begin the alternate method from the service’s own screen.
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When authentication fails because of a technical problem, biometric limitation, illness, injury, infirmity, or another specified reason, the requesting entity must provide an alternate and viable means of identification under Section 8(3) of the Aadhaar Act. The provision states: “Provided that the requesting entity shall, in case of failure to authenticate due to illness, injury or infirmity owing to old age or otherwise or any technical or other reasons, provide such alternate and viable means of identification of the individual, as may be specified by regulations.”
UIDAI’s resident FAQ likewise says providers must have exception handling so that people are not denied entitlements because of technological or biometric limitations. This does not mean every private service offers the same alternative; it means you should explicitly ask for the process instead of abandoning the service after a failed match.
- Show the operator the exact error code and explain whether you used OTP or biometrics.
- Ask what alternate identification or exception-handling route is available for that service.
- Follow the provider’s documented verification steps and keep any acknowledgement or reference number.
- If the operator refuses to explain the alternative, record the date, location, service, and staff contact and escalate through the provider’s grievance channel or UIDAI’s help and grievance resources.
What to include when escalating
A useful escalation contains enough context for the operator to find the failed transaction without exposing unnecessary personal data.
- The exact numeric error code and the full accompanying message.
- The service name, outlet or portal, and the step at which authentication failed.
- The authentication modality: OTP, fingerprint, iris, or face.
- The date and approximate time, including your time zone if the service is remote.
- Whether you pressed Resend, refreshed, used Back, changed tabs, or changed networks.
- Whether a new transaction was attempted and which code it returned.
Never send an OTP, password, or a full Aadhaar number in an unsolicited message. The operator can usually locate the request from the code, time, and transaction reference, then ask for additional information through its approved channel.
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No physical product is required to correct these failures. A PVC Aadhaar card does not repair an invalid OTP, a stale session, a biometric mismatch, or an unavailable record. Scanners and registered-device equipment are operator infrastructure, and OTPs are generated by the service transaction. Buying a card, book, form, or unrelated authenticator app will not change the UIDAI error code. Use the code-specific recovery, the service provider’s technical support, or the legally required alternate-identification route.
Quick Recap
A compact decision path
- Code 400: enter the current six-digit OTP; request a fresh one after repeated failures.
- Code 402: restart so the OTP and transaction ID are created together.
- Code 403: generate a fresh OTP from a new transaction; escalate if the limit condition returns.
- Code 740: wait for the response and enter all six digits before submitting.
- Code 952: stop requesting codes, wait, then make one new request after the resend interval.
- Code 504 or a timeout: discard the stale session, avoid Refresh and Back, and start again with a stable connection.
- Biometric failure: clean the finger and scanner, correct placement and pressure, try another finger, then request a biometric update or another modality if failures persist.
- Code 998: check the Aadhaar number format; ask the provider to investigate unavailable data if the number is correct.
- Any unresolved failure: retain the code and request exception handling or alternate identification from the concerned entity.
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